Risk Factors Associated with the Halo Phenomenon after Lumbar Fusion Surgery and its Clinical Significance

STUDY DESIGN Retrospective study. PURPOSE First, to examine the association between bone mineral density (BMD) and the halo phenomenon, and second, to investigate risk factors predisposing to the halo phenomenon and its correlation with clinical outcomes. OVERVIEW OF LITERATURE The few in vivo studies regarding the relationship between pedicle screw stability and BMD have shown conflicting results. METHODS Forty-four female patients who underwent spine fusion surgery due to spinal stenosis were included in this study. The halo phenomenon and fusion state were evaluated through plain radiographs performed immediately after surgery and through the final outpatient follow-up examination. BMD, osteoarthritis grade in the hip and knee joints, and surgical outcome were also evaluated. RESULTS BMD was not related to the halo phenomenon, but age, absence of osteoarthritis in the knee, and non-union state were found to be significant risk factors for the halo phenomenon. However, the radiological halo phenomenon did not correlate with clinical outcome (visual analogue scale for back pain and leg pain). CONCLUSIONS The halo phenomenon is a simple phenomenon that can develop during follow-up after pedicle screw fixation. It does not influence clinical outcomes, and thus it is thought that hydroxyapatite coating screws, expandable screws, cement augmentation, and additional surgeries are not required, if their purpose is to prevent the halo phenomenon.